1. Field of the Invention
One embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the invention disclosed in this specification and the like relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the invention disclosed in this specification and the like relates to a semiconductor device and an electronic device including the semiconductor device.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A display device (e.g., a liquid crystal display device and a light-emitting display device), a lighting device, an electro-optical device, a power storage device, a memory device, a semiconductor circuit, an imaging device, an electronic device, and the like may include a semiconductor device.
2. Description of the Related Art
In recent years, transistors including an oxide semiconductor (OS) for a semiconductor layer where a channel is formed (the transistor is also referred to as “OS transistor”) have attracted attention. An oxide semiconductor can be formed by a sputtering method or the like, and thus, for example, can be used for a semiconductor layer of a transistor in a large display device. In addition, there is an advantage that capital investment can be reduced because the OS transistor can be utilized for part of retrofitted production equipment for a transistor including amorphous silicon in a semiconductor layer where a channel is formed.
The OS transistor is known to have an extremely low leakage current in an off state. For example, a low-power-consumption CPU and the like utilizing the characteristics that a leakage current of the OS transistor is extremely low is disclosed (see Patent Document 1).